Oscillating sander

ABSTRACT

An oscillating sander includes a housing and a tool holder which receives a sanding plate and sits via a rotary bearing on a rotating eccentric stem that projects from the housing and is attached flexibly against rotary entrainment on the housing by way of at least one oscillating, element. The oscillating is assembled from two hard-elastic rings, one outer ring and one inner ring, made in particular of plastic and arranged spaced apart from one another and in particular concentrically, which are coupled to one another, with minimally limited radial displaceability with respect to one another and with limited rotatability with respect to one another, via an elastic spacer element, the spacer element being made of soft plastic equipped with openings.

FIELD OF THE INVENTION

The present invention relates to an oscillating sander and to anoscillating element of the oscillating sander.

BACKGROUND INFORMATION

European Patent Application No. 0 610 801 describes a conventionaloscillating sander of the species whose tool holder is coupled onto thehousing via a flexible oscillating element, the known oscillatingelements being of elongated T-shaped configuration, and beingrespectively attached with their long, rod-shaped center web to the toolholder, and standing out at right angles therefrom and restingpositively in recesses of the housing.

Because of the elongated shape of the known oscillating elements, thespacing of the tool holder from the housing is so great that the deviceis relatively less than compact, and the operator's hand is relativelyfar away from the workpiece being processed, so that it is thusdifficult to process sensitively.

SUMMARY OF THE INVENTION

A oscillating sander according to the present invention has theadvantage that as a result of the disk-shaped configuration, accordingto the present invention, of the oscillating element, the spacingbetween the tool holder and the housing can be kept considerably smallerthan in the previously known art. The bearing spacings between thehousing and the tool holder for the output shaft can accordingly also bekept small. The tilting moment acting on the bearings is consequentlyminimized, so that the output shaft can be made smaller and lighter.

The oscillating sander can thus be handled more sensitively, andworkpieces can be processed particularly accurately with it.

The oscillating element according to the present invention meets, theneed for minimum possible rotatability of the tool holder or tool withrespect to the housing, along with a particularly smooth-running,minimally limited orbital oscillating motion of the tool holder with thetool during sanding operations. This ensures effective material removalwhen sanding in poorly accessible corners and flutes if the tool isapplied especially firmly or at a tilt onto the workpiece, and reducesthe load on the rotary bearings.

The oscillating element according to the present invention provides acompact and flat design for the oscillating sander, and excludes fromthe housing and from the lower bearing of the working shaft any sandingdust arriving from below. The oscillating element according to thepresent invention can moreover be mounted particularly easily on theoscillating sander by axially inserting the parts into one.

SUMMARY OF THE INVENTION

Because the oscillating element includes an outer ring and an innerring, which are joined to one another by a spacer element made up ofspoke-like ribs running obliquely with respect to a radial line,particularly hard limits are placed on rotation of the sanding platewith respect to the housing, the eccentric motion being guided andcushioned especially softly. This reduces the load on the working shaftbearings. According to, another exemplary embodiment of the prsentinvention because, the spacer element is made of a rubber-like,injectable soft plastic with regular openings, certain regions of thespacer element can, upon deformation as a result of rotation of the toolwith respect to the housing, enter into the deflection spaces thuscreated, thereby achieving a controlled spring characteristic similar tothat with spoke-like ribs.

In addition, the openings in the spacer element result in the formationof correspondingly dimensioned and oriented ribs with which thedifferent spring characteristic of the spacer element can be even betterdefined between hard rotational delimitation and soft radialdelimitation.

Because the inner ring has lobes projecting radially outward, and theouter ring has counterlobes pointing radially inward and overlapping thelobes, the rotatability of the inner ring with respect to the outer ringis delimited by positive engagement; the spacer element is immobilizedbetween the lobes and counterlobes and can be compressed en bloc byrotation of the outer ring with respect to the inner ring, for exampleby rotation of the tool with respect to the housing, thereby limitingthe rotation of the rings with respect to one another so thatoverloading of or damage to the spacer element can be prevented.

Because the oscillating element is a replaceable spare part that, by wayof its configuration, critically influences the function of theoscillating sander, this part has a distinct inventive significance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial longitudinal section of a front region of aoscillating sander according to the present invention.

FIG. 2 shows a perspective view of the oscillating element illustratedin FIG. 1.

FIG. 3 shows a plan view of the oscillating element illustrated in FIG.1 .

FIG. 4 shows an outer ring of the oscillating element illustrated inFIG. 3.

FIG. 5 shows a plan view of an inner ring of the oscillating elementillustrated in FIG. 3.

FIG. 6 shows a bottom view of the inner ring.

FIG. 7 shows a plan view of another exemplary embodiment of theoscillating element.

FIG. 8 shows a cross section of the oscillating element illustrated inFIG. 7.

FIG. 9 shows a cross section of an oscillating element formed from adoubled arrangement of the oscillating element illustrated in FIG. 7.

FIG. 10 shows a plan view of the oscillating element illustrated in FIG.9.

FIG. 11 shows another exemplary embodiment of the oscillating element.

FIG. 12 shows a further exemplary embodiment of the oscillating element.

DETAILED DESCRIPTION

Oscillating sander 10 shown in partial longitudinal section in FIG. 1 isconfigured as a delta sander, and has a triangular, symmetrical sandingplate 12. Sanding plate 12 is made of plastic, and its underside isequipped with a hook-and-loop pad 14 for receiving a sandpaper sheet 14.Delta sander 10 can selectably be fitted with a conventional rectangularsanding plate known per se, with a round sanding disk, or with othersanding tools, for example a flap-wheel sanding attachment or a sandingtongue or sanding roller.

Delta sander 10 possesses a housing 18 which carries an electric motor20, of which only a fan 24 sitting on its output shaft 22 is visible inFIG. 1. A slide switch 26 arranged on the upper side of housing 18serves to switch electric motor 20 on and off. Output shaft 22 drives,via a right-angle drive train 28, a working shaft 30 which is rotatablymounted in two housing-mounted ball bearings 32 and 33, and projects outof housing 18, from the lower end face of housing 18, with an eccentricstem 36. Sitting on eccentric stem 36 is a tool holder 38 which carriesa pressed-in ball bearing 21 and on its underside nonrotatably andaxially nondisplaceably receives sanding plate 12. Tool holder 38 andsanding plate 12 are matched to one another in terms of shape, so thatsanding plate 12 rests in planar fashion against tool holder 38. Toolholder 38 is fastened via a flexible oscillating element 42 to housing18, and thus protected from being rotationally entrained by the rotatingeccentric stem 36.

When electric motor 20 is switched on using slide switch 26, the motordrives working shaft 30, via right-angle drive train 28, so that itrotates about its axis 31. Eccentric stem 36, whose axis 37 is offsetfrom axis 31 of working shaft 30 by a distance equal to eccentricdimension e, performs a circular motion as working shaft 30 rotates,thus imparting to tool holder 38, together with sanding plate 12 andsandpaper sheet 16, an orbiting motion in which it is prevented byoscillating element 42 from rotating about its own axis.

Oscillating element 42, which is depicted in detail in FIGS. 2 through8, is configured as a ring which fits with its radially internallylocated region around tool holder 38, and whose radially externallylocated region is attachably encompassed by housing 18. Oscillatingelement 42 has an inner ring 44 and an outer ring 46 spaced apartconcentrically therefrom, as well as an annular spacer element 48 madeof flexible material, for example silicone. This spacer element 48 joinsthe inner 44 and outer ring 46 to one another. Inner ring 44 and outerring 46 are made of plastic, and annular spacer element 48 ismanufactured from rubber or from an injectable soft plastic. Siliconehas particularly temperature-stable characteristics.

FIGS. 2 and 3 show the annular spacer element 48 with axially continuousslot-like openings 50 and 52 which pass through spacer element 48uniformly, as if on a reference circle, radially farther inward andfarther outward. Openings 50, 52 are each closely radially adjacent tofour radially outward-facing lobes 60 of inner ring 44, and to fourradially inward-facing counterlobes 64 of outer ring 46. Lobes 60 andcounterlobes 64 overlap one another in the radial direction and engage,like a toothed hub or shaft, into tooth gap-like spaces 62 and 66located respectively opposite them.

Inner ring 44 is attached on tool holder 38 coaxially with ball bearing40, and outer ring 46 is held nonrotatably in housing 18 by positiveengagement. For this purpose, outer ring 46 carries on its exterior,arranged in a manner distributed over the circumference, integral lugs68, 70 which can be placed, in a manner secured against loss, intocorresponding grooves 80, 81 arranged in housing 18. Of the six radialexternal lugs 68, 70 shown the two external lugs 68 locateddiametrically opposite one another are of T-shaped configuration, withtheir respective center webs 75 extending radially out from outer ring46.

Inner ring 44 is slid onto an annular fitting 39 that is configured onthe upper side of tool holder 38 coaxially with axis 37 of eccentricstem 36, and joined immovably thereto, for example welded or adhesivelybonded. For accurate alignment of oscillating element 42 when beingplaced onto annular fitting 39, integrally shaped-on axial positioninglugs 56 (FIG. 2) are arranged, distributed over the circumference, onthe lower end face of inner ring 44, and when oscillating element 42 isplaced onto annular fitting 39 they enter positively into correspondingrecesses on annular fitting 39 and create a positive connection which issecured against undesired detachment.

Inner ring 44 can also be axially joined to tool holder 38 in adifferent fashion, e.g. can be welded.

FIG. 4 shows a plan view of outer ring 46 of oscillating element 42, theradially inward-facing lobes 64, spaces 66, and radial external lugs 68being clearly shown.

FIG. 5 shows a plan view from below of inner ring 44 of oscillatingelement 42, with the four radially outward-facing lobes 60 and recesses62.

FIG. 6 shows inner ring 44 from below, indicating the axial positioninglugs 56 which positively and releasably define the position ofoscillating element 42 with respect to tool holder 38.

FIG. 7 shows a further exemplary embodiment of an oscillating element142 which includes an outer ring 146 and an inner ring 144 that arejoined to one another by spacer members, extending in obliquely curvedfashion, in the form of three spokes 148.

FIG. 8 shows a cross section of oscillating element 142 according toFIG. 7; the cavities between the spoke-like spacer members 148 can beopen or can be additionally filled by injection with silicone or thelike.

FIGS. 9 and 10 show a further oscillating element 242, assembled fromtwo oscillating elements 142 according to FIGS. 7 and 8, which securesinner ring 244 even more effectively against rotation with respect toouter ring 246.

FIG. 10 shows a plan view of oscillating element 242 according to FIG.10, clearly indicating that spoke-like spacer members 148 run inopposite directions.

FIG. 11 shows a further oscillating element 342, including outer ring346 and inner ring 344, whose spacer member 348 possesses regularopenings 350 extending in circular fashion, the arrangement of whichimparts a particular spring characteristic to the remaining material ofspacer element 348.

FIG. 12 shows an exemplary embodiment of an oscillating element 442which is similar to ascillation element 342 shown in that according FIG.11; openings 350 in spacer member 448 of oscillating element 442 aresmaller than in spacer member 348 and have, regardless of the type ofmaterial chosen for spacer member 448, a different spring characteristicmore suitable for certain applications.

In an exemplary embodiment of an oscillating element that is notdepicted, two hard-elastic rings substantially of equal size, axiallyspaced apart and joined to one another by an elastic spacer ring whichfills up the axial cavity, are provided, the lower ring being joinableto the tool holder and the upper ring to the housing of the oscillatingsander. It is also possible, in this exemplary embodiment, to provideaxially projecting lugs which overlap one another axially, lie onapproximately the same circle diameter, and serve, when the rings rotatewith respect to one another, as stops which limit rotation. The springcharacteristic achievable therewith is of similar quality to that withthe radially concentrically arranged outer and inner rings of thepreviously described exemplary embodiments.

What is claimed is:
 1. An oscillating sander, comprising:a housing; arotating eccentric stem projecting from the housing; a rotary bearing; atool holder disposed on the rotating eccentric stem via the rotarybearing; and at least one oscillating element flexibly attaching thetool holder to the housing for preventing the tool holder from followinga rotation of the rotating eccentric stem, the at least one oscillatingelement including an elastic spacer element and two hard-elastic ringscomposed of a plastic material, the elastic spacer element havingopenings, wherein a first of the hard-elastic rings is spaced at apredetermined distance from a second of the hard-elastic rings, the twohard-elastic rings being radially and displaceably coupled to oneanother via the elastic spacer element, and wherein the firsthard-elastic ring is rotatable with respect to the second hard-elasticring in a limited predetermined manner.
 2. The oscillating sanderaccording to claim 1, wherein the hard-elastic rings have a cavitytherebetween, the cavity being filled in a flush manner by the elasticspacer element.
 3. The oscillating sander according to claim 1, whereinthe two hard-elastic rings are situated concentrically, the firsthard-elastic ring being an outer ring and the second hard-elastic ringbeing an inner ring.
 4. The oscillating sander according to claim3,wherein the elastic spacer element is composed of an injectable softplastic material, wherein the openings in the elastic spacer elementhave an elongated configuration and extend in a particular orientationwhich is perpendicular to radials, and wherein the at least oneoscillating element includes ribs which are provided between theopenings in the elastic spacer element, the ribs defining a first springaction in a circumferential direction and a second spring action in aradial direction, the first and second spring actions being definedbetween the outer ring and the inner ring.
 5. The oscillating sanderaccording to claim 3,wherein the inner ring includes radiallyoutward-facing protruding lobes, the protruding lobes being provided ata first spacing from one another, wherein the outer ring includesradially inward-facing counterlobes, the counterlobes being provided ata second spacing from one another, and wherein the protruding lobespenetrate into the second spacing, and the counterlobes penetrate intothe first spacing so that one of the protruding lobes and thecounterlobes overlaps another one of the protruding lobes and thecounterlobes.
 6. The oscillating sander according to claim 5, whereinthe elastic spacer element is immobilized between the protruding lobesand the counterlobes, the elastic spacer element being completelycompressible by rotating the outer ring with respect to the inner ringfor limiting a rotation of the hard-elastic rings with respect to oneanother.
 7. The oscillating sander according to claim 6, wherein theelastic spacer element is compressed by rotating a tool received by thetool holder with respect to the housing.
 8. The oscillating sanderaccording to claim 1, wherein the tool holder receives a sanding plate.9. The oscillating sander according to claim 1, wherein the hard-elasticrings are concentrically spaced apart from one another.
 10. Anoscillating sander, comprising:a housing; a rotating eccentric stemprojecting from the housing; a rotary bearing; a tool holder disposed onthe rotating eccentric stem via the rotary bearing; and at least oneoscillating element flexibly attaching the tool holder to the housingfor preventing the tool holder from following a rotation of the rotatingeccentric stem, the at least one oscillating element including anelastic spacer element and two hard-elastic rings composed of a plasticmaterial, the elastic spacer element including spoke-shaped ribsextending obliquely with respect to a radial direction of thehard-elastic rings, wherein a first of the hard-elastic rings is spaceda predetermined distance from a second of the hard-elastic rings, thehard-elastic rings being radially and displaceably coupled to oneanother via the elastic spacer element, and wherein the firsthard-elastic ring is rotatable with respect to the second hard-elasticring in a limited predetermined manner.
 11. The oscillating sanderaccording to claim 10, wherein the first hard-elastic ring is an outerring and the second hard-elastic ring is an inner ring.
 12. Theoscillating sander according to claim 11, wherein the first and secondhard-elastic rings are concentric.
 13. The oscillating sander accordingto claim 10, wherein the tool holder receives a sanding plate.
 14. Anoscillating element of an oscillating sander, the oscillating sanderincluding a housing, a rotating eccentric stem projecting from thehousing, a rotary bearing, and a tool holder disposed on the rotatingeccentric stem via the rotary bearing, the oscillating element flexiblyattaching the tool holder to the housing for preventing the tool holderfrom following a rotation of the rotating eccentric stem, theoscillating element comprising:an elastic spacer element havingopenings; and two hard-elastic rings composed of a plastic material,wherein a first of the hard-elastic rings is spaced at a predetermineddistance from a second of the hard-elastic rings, the two hard-elasticrings being radially and displaceably coupled to one another via theelastic spacer element, and wherein the first hard-elastic ring isrotatable with respect to the second hard-elastic ring in a limitedpredetermined manner.
 15. The oscillating element according to claim 14,wherein the two hard-elastic rings are situated concentrically, thefirst hard-elastic ring being an outer ring and the second hard-elasticring being an inner ring.
 16. The oscillating element according to claim15,wherein the elastic spacer element is composed of an injectable softplastic material, wherein the openings in the elastic spacer elementhave an elongated configuration and extend in a particular orientationwhich is perpendicular to radials, and wherein the at least oneoscillating element includes ribs which are provided between theopenings in the elastic spacer element, the ribs defining a first springaction in a circumferential direction and a second spring action in aradial direction, the first and second spring actions being definedbetween the outer ring and the inner ring.
 17. The oscillating elementaccording to claim 15,wherein the inner ring includes radiallyoutward-facing protruding lobes, the protruding lobes being provided ata first spacing from one another, wherein the outer ring includesradially inward-facing counterlobes, the counterlobes being provided ata second spacing from one another, and wherein the protruding lobespenetrate into the second spacing, and the counterlobes penetrate intothe first spacing so that one of the protruding lobes and thecounterlobes overlaps another one of the protruding lobes and thecounterlobes.
 18. The oscillating element according to claim 17, whereinthe elastic spacer element is immobilized between the protruding lobesand the counterlobes, the elastic spacer element being completelycompressible by rotating of the outer ring with respect to the innerring for limiting a rotation of the hard-elastic rings with respect toone another.
 19. The oscillating element according to claim 14, whereinthe first hard-elastic ring is an outer ring and the second hard-elasticring is an inner ring.
 20. The oscillating element according to claim14, wherein the first and second hard-elastic rings are concentric. 21.The oscillating element according to claim 14, wherein the tool holderreceives a sanding plate.
 22. An oscillating element of an oscillatingsander, the oscillating sander including a housing, a rotating eccentricstem projecting from the housing, a rotary bearing, and a tool holderdisposed on the rotating eccentric stem via the rotary bearing, theoscillating element flexibly attaching the tool holder to the housingfor preventing the tool holder from following a rotation of the rotatingeccentric stem, the oscillating element comprising:an elastic spacerelement; and two hard-elastic rings composed of a plastic material, theelastic spacer element including spoke-shaped ribs extending obliquelywith respect to a radial direction of the hard-elastic rings, wherein afirst of the hard-elastic rings is spaced at a predetermined distancefrom a second of the hard-elastic rings, the hard-elastic rings beingradially and displaceably coupled to one another via the elastic spacerelement, and wherein the first hard-elastic ring is rotatable withrespect to the second hard-elastic ring in a limited predeterminedmanner.
 23. The oscillating element according to claim 22, wherein thefirst hard-elastic ring is an outer ring and the second hard-elasticring is an inner ring.
 24. The oscillating element according to claim23, wherein the first and second hard-elastic rings are concentric. 25.The oscillating element according to claim 22, wherein the tool holderreceives a sanding plate.